It is highly desirable to provide a relatively low cost copper base alloy which will obtain a combination of high electrical conductivity with favorable strength and ductility characteristics and with excellent softening resistance.
Modern applications, for example in the electronics industry for lead frames, heat sinks and other electrical connectors, place many stringent requirements on copper base alloys. These electronic devices, for example, must withstand elevated temperature excursions without softening during manufacture. In addition, applications such as aforesaid require high thermal conductivity and good softening resistance while retaining high strength. Other applications also place stringent requirements on copper base alloys while, of course, emphasizing moderate cost.
Thus, it is highly desirable to provide copper base alloys which have high thermal and electrical conductivities together with good strength and good bend formability and resistance to fracture during multiple bending. Specifically, it would be highly desirable to provide copper base alloys which are characterized by moderate cost and which are capable of obtaining a 90% IACS electrical conductivity together with good softening resistance and a good combination of strength to bend properties.
U.S. Pat. Nos. 3,677,745 and 3,778,318 teach a copper base alloy containing defined amounts of magnesium and phosphorus together with preferred additions of silver and/or cadmium. Naturally, the silver addition in such an alloy represents a high cost factor. In addition, it has been found that the alloy of these patents, while obtaining good electrical conductivity, can be deficient in softening resistance.
In addition to the foregoing, the art teaches that high conductivity and high softening resistance may be obtained with copper base alloys containing zirconium such as U.S. Pat. Nos. 3,143,442 and 3,392,016. However, it has been found that these alloys are lacking in good strength/formability characteristics. U.S. Pat. No. 3,698,965 teaches a high strength copper alloy containing defined amounts of iron, cobalt and phosphorus plus magnesium and/or tin; however, the conductivity of this alloy falls only in the 50 to 60% IACS range.
Accordingly, it is a principal object of the present invention to provide improved copper base alloys having a good combination of conductivity and strength characteristics.
It is a further object of the present invention to provide such a copper base alloy which is characterized by high electrical and thermal conductivity together with favorable strength and ductility combinations and also with excellent softening resistance.
It is a further object of the present invention to provide an alloy as aforesaid which is relatively inexpensive and which may be conveniently processed.
Further objects and advantages of the present invention will appear hereinbelow.